Authors

Disclosure statement

Chrystal Mantyka-Pringle received funding from the Australian Government's National Environmental Research Program, the Australian Research Council Centre of Excellence for Environmental Decisions, and the Canadian Water Network. Chrystal is affiliated with the University of Queensland, CSIRO and the University of Saskatchewan.

Jonathan Rhodes receives funding from the Australian Research Council and the Australian, Queensland and New South Wales Governments.

Tara Martin does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Freshwater covers a tiny area of the planet’s surface, but is vital for our economies, environment and, of course, our survival. Yet freshwater is also among the most threatened ecosystems, where wildlife has declined faster than in the oceans or on land.

Water is life

According to the United Nations, more than 40% of the global workforce is heavily dependent on freshwater. There are strong links between water and jobs across all sectors of the economy – agriculture, fisheries and forestry, energy, manufacturing and transport.

All ecosystems are connected by water. As a result freshwater is worth trillions of dollars to our economy through various ecosystem services. These include power generation, food and medicine production, flood buffering and recreation and tourism.

Freshwater threats

Of all the Earth’s ecosystems, freshwater ecosystems have been hit hardest by human activities. Key threats include dams, farming and industry, water extraction, pollution, flow change, invasive species, over-harvesting of species, and climate change.

To make the management of freshwater ecosystems even more challenging, these threats often interact in ways that are difficult to predict. These complex and interacting threats are often ignored, leading to poor decisions and ultimately the loss of species.

Habitat loss and degradation are primarily due to deforestation, farming activities and dams. When these activities occur in an upper-catchment area, sediment is carried into rivers and lakes, causing significant negative impacts on freshwater species.

Unsustainable water extraction – for irrigation, industry and urban consumption – is a major threat to freshwater species. Over-harvesting of freshwater species (particularly fish) is, in turn, a threat to these ecosystems.

Infrastructure development – including dams and levees – also modifies water flow. There are perhaps one million dams globally, fragmenting rivers into isolated sections. Freshwater species – including fish, molluscs and reptiles – often can’t adapt to these changes and are at increased risk of extinction.

Pollution is another significant threat to these habitats. Fertiliser runoff from farming and the dumping of industrial pollutants directly into rivers and lakes have resulted in areas so poisoned that they can no longer support their normal range of species.

Invasive species have played a major role in disrupting freshwater ecosystems. The European carp (Cyprinus carpio), for example, is a pest that out-competes native fish. It was first introduced to Australian waterways more than 100 years ago and has spread to every state and territory except the Northern Territory. The federal government has recently taken steps to control carp, by way of plans to introduce a herpes virus.

Climate change presents another threat to freshwater habitats, particularly to those species that can’t migrate or compensate for higher temperatures. In Australia, extreme weather fluctuations and natural disasters such as floods and droughts are projected to become more common, placing freshwater biodiversity under further stress.

As threats intensify and interact in the coming decades, the risk to freshwater wildlife will increase. Vulnerable freshwater ecosystems in Australia such as the Murray-Darling Basin will be particularly susceptible to further loss of species.

So how do we decide what actions to take to best protect and restore our freshwater ecosystems?

But this can be expensive. We can make it cheaper to protect freshwater wildlife by including farm and land management – such as rotating pasture, reducing erosion through smart burning practices, and better management of pesticides and nutrients.

While changing farm and land-use practices around rivers can improve water quality “cheaply”, these may have only a modest effect on biodiversity overall – especially if the land next to rivers is degraded.

We have seen such improvements in a few catchments throughout Australia such as in Queensland. Yet many other catchments nationally continue to deteriorate in water quality and biodiversity.

We therefore cannot just target best-practice farm management programs in the hope that our farmers will do what’s best for the land and biodiversity. We all need to share in the cost of restoring our freshwater ecosystems.